Responses of detoxification enzymes in Rhizoglyphus robini (Acari: Acaridae) after exposure to imidacloprid
Paper ID : 1020-IPCA4 (R1)
sara alimirzaee *1, Jahangir Khajeali2
1Department of Plant Protection, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
2Associate Professor, Department of Plant Protection, College of Agriculture, Isfahan University of Technology, Isfahan
Detoxification enzymes such as Cytochrome P450 enzymes, Glutathione S-transferases, and esterases play important roles in the metabolism of insecticides in insects and mites. These enzymes possess the capacity for rapid increases in activity in response to chemical stress, a phenomenon known as enzyme induction. Here, the phenomenon of enzyme induction was investigated in Rhizoglyphus robini, an important pest of saffron as a strategic crop in Iran, in response to pre-treatment with imidacloprid as the most successful and leading molecule of neonicotinoid insecticides. For this purpose, five different concentrations of imidacloprid including 0, 35, 70, 140 and 280 mg a.i./l were selected. At each concentration, a group of females with a maximum age of 48 hours were treated with imidacloprid concentrations for 48 hours and then transferred to insecticide-free containers. Activities of detoxifying enzymes, P450s, GSTs, and esterases were evaluated at two time intervals of 0 and 48 hours after insecticide treatment. Immediately after treatment, P450s activity significantly increased in mites treated with 140 and 280 mg a.i./l, while 48 hours after treatment, a significant induction of P450s was observed at 280 mg a.i./l. Induction of esterases was observed immediately after treatment only at 70 mg a.i./l and no significant change was observed 48 hours after treatment in the esterase activity of treated mites. The highest activity of GSTs at zero time after treatment was observed at 70, control and 35 mg a.i./l concentrations, respectively, while at 48 hours after treatment an increase in the GST activity was observed at 280 mg a.i./l. Due to the fact that the metabolism of neonicotinoids in the first phase is largely dependent on P450s, a 1.5 fold increase in P450 activity compared to the controls was observed immediately after treatment with 280 mg a.i./l imidacloprid. While such an increase was observed in GST activity, a phase two detoxification enzymes, 48 hours after imidacloprid treatment. The results showed that the time after exposure and the insecticide concentration may significantly affect the levels of enzyme induction.
Enzyme induction, Bioassay, Acari, Detoxification enzymes, Rhizoglyphus robini
Status : Abstract Accepted (Poster Presentation)